1. Field of the Invention
The present invention relates to a position sensing liquid crystal display (PSLCD), and more particularly to a position sensing liquid crystal display and a method for fabricating the same, in which position sensors, such as digitizers, are formed after bonding of upper and lower plates of the liquid crystal display.
2. Discussion of the Related Art
In general, the liquid crystal display at large is provided with an upper plate, a lower plate, and a liquid crystal sealed between the upper plate and the lower plate. The upper plate has a black matrix layer, a common electrode, and color filter layers of R(red), G(green), and B(blue) for displaying colors disposed thereon. The lower plate has data lines and gate lines crossing the other to form a matrix of pixel regions, each having a thin film transistor and a pixel electrode. That is, as shown in FIG. 1, the lower plate 1 is provided with a matrix of thin film transistors, each having a gate electrode gate extended from a scan line, a source electrode S and a drain electrode extended from a data line disposed at fixed intervals. Each of the pixel regions is provided with a pixel electrode 2a having the drain electrode D of the thin film transistor 2 connected thereto. The upper plate 3 is provided with a matrix form of the black matrix layer 4 for blocking transmission of light for parts excluding the pixel electrodes 2a on the lower plate 1. There are R, G, and B color filter layers 5 between the black matrix layer 4, each for displaying a color. A common electrode 6 is formed extended to the color filter layer 5 and the black matrix layer 4. Upon selective application of driving signals to the scanning lines and the data lines from external driving circuits, the liquid crystal display displays an image. Though the aforementioned liquid crystal display has been designed only to display images according to the external driving signals, recently researches are underway in which the liquid crystal display is provided with additional position sensors for efficient use of the display in a notebook computer. That is, if a character or graphic is drawn with a stylus (an electronic pen) on the liquid crystal display equipped with the position sensors, the character or graphic is displayed as drawn.
A related art position sensing liquid crystal display will be explained with reference to the attached drawings. FIG. 2 illustrates a first example of the related art position sensing liquid crystal display.
Referring to FIG. 2, the first example of the related art position sensing liquid crystal display has a digitizer for sensing a position additionally provided outside of a general liquid crystal display independently, i.e., provided with a liquid crystal display 21 and a digitizer panel 23. There is a position sensing layer 23a (hereafter called, xe2x80x9cdigitizerxe2x80x9d), a compensating resistor region 25 around the digitizer 23a for compensating a voltage difference, and signal applying parts 27a, 27b, 27c, and 27d at four corners of the compensating resistor region 25 for applying a position sensing signal. In the aforementioned position sensing liquid crystal display, when the signal applying parts 27a and 27b are applied at a position signal and the signal applying parts 27c and 27d are grounded, the digitizer 23a has a potential distribution from upper side to lower side thereof. When the signal applying parts 27a and 27c are applied at a position signal and the signal applying parts 27b and 27d are grounded, the digitizer 23a has a potential distribution from right side to left side thereof. Thus, when a stylus 29 is brought into contact with a point on the digitizer 23a after selective application of a position sensing signal to the signal applying parts 27a, 27b, 27c, and 27d, a present position of the stylus 29 can be sensed and determined. In the sensing of the position, a voltage of the position of the digitizer 24a at which the stylus 29 is brought into contact is used. The position sensing of even a finger tip touch can be made, which is displayed in turn on a liquid crystal display.
FIG. 3 illustrates a second example of the related art position sensing liquid crystal display. The second PSLCD has a position sensing digitizer provided inside a liquid crystal display panel. As explained in connection with FIG. 1, the second PSLCD is provided with metal, an insulating film, and a semiconductor layer on a glass for displaying an image, wherein a position sensing layer is embodied using the glass of an image data input electrical device. That is, the second PSLCD is provided with an upper plate 21a, a lower plate 21b, and a digitizer 23a between the upper plate 21a and the lower plate 21b. As explained, the upper plate 21a has the black matrix layer (not shown), a color filter layer, and an ITO layer of a common electrode formed thereon. The lower plate 21b has data lines 31, gate lines 33, and pixel electrodes (not shown), and the digitizer 23a has a compensating resistor region 25 around the digitizer and signal applying parts 27b and 27d at four corners of the compensating resistor region 25 (signal applying parts 27a and 27c are not shown).
In the second PSLCD, when the signal applying parts 27a, 27b, 27c, and 27d are applied of a position signal, the digitizer 23a exhibits a potential distribution. Accordingly, when stylus 29 is brought into contact with the display, a voltage at the contact point is sensed, thereby allowing to sense the present position. A finger tip touch on the display can be also sensed. Thus, when a stylus 29 is brought into contact with a position sensing digitizer 23a after selective application of position signal through signal applying parts 27a, 27b, 27c, and 27d, the PSLCD can sense the present position of the stylus 29 by using a capacitive coupling between the digitizer 23a and the stylus 29.
However, the aforementioned related art PSLCD has the following problems. First, the first PSLCD is cumbersome to carry because of the digitizer provided additionally on the outside of the LCD, which makes the LCD thicker and bulkier.
Second, in the case of the second PSLCD, the severe signal interference and the non-uniform potential distribution of a position sensing layer caused by capacitive coupling between the position sensing layer in the digitizer and the common electrode disposed on opposite sides of an insulating film impedes accurate position sensing and degrades the picture quality.
Third, in a case of the first conventional PSLCD, the inaccurate voltage compensation caused by the misaligned digitizer with respect to the panel causes an inaccurate position sensing.
Accordingly, the present invention is directed to a position sensing liquid crystal display and a method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a position sensing liquid crystal display and a method for fabricating the same which can sense an accurate position of the stylus.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display panel has a first substrate having front and rear surfaces, a second substrate having front and rear surfaces, the front surface of the second substrate including a plurality of pixel electrodes and abutting against the rear surface of the first substrate, and a digitizer having intersecting grids fabricated on at least one of the front and rear surfaces of the first and second substrates.
According to one aspect of the present invention, the rear surface of the first substrate includes a black matrix layer having intersecting grids at a predetermined interval. Preferably, the digitizer is fabricated on the front surface of the first substrate, the intersecting grids of the digitizer being substantially aligned with the intersecting grids of the black matrix layer. The intersecting grids of the digitizer may be made of a conductive material, such as metal or Indium Tin Oxide. Instead of providing a digitizer separate from the black matrix, the intersecting grids of the black matrix layer may be used as the intersecting grids of the digitizer, in which the intersecting grids of the black matrix layer are fabricated with a conductive material.
In another aspect of the present invention, the digitizer may be fabricated on the rear surface of the second substrate, the intersecting grids of the digitizer being substantially aligned with the intersecting grids of the black matrix layer.
In another aspect of the present invention, input signal portions may be fabricated in the vicinity of four corners of the digitizer. The input signal portions provide a position signal, such as an input voltage, to the intersecting grids of the digitizer for detecting a stylus position. Alternatively, the input signal portions may be fabricated substantially in the middle of each side of the digitizer.
In the liquid crystal display panel with the digitizer according to the present invention, there are compensating resistors connected between the input signal portions and the intersecting grids of the digitizer. The compensating resistors formed near the input signal portions preferably have a higher resistivity than the compensating resistors formed farther away from the input signal portions to provide substantially equal potential to the intersecting grids of the digitizer. The compensating resistors include a tree shape of repetitive sequence of layers of primary interconnections between adjacent grids, secondary interconnections between adjacent primary interconnections, and tertiary interconnections between adjacent secondary interconnections.
In addition, there is at least one equipotential line connected between the input signal portions and the compensating resistors. Preferably, the equipotential line has a lower resistivity than the compensating resistors.
The PSLCD having a digitizer may be used with a controller that controls displayed images of the liquid crystal display panel. Such controller is necessary for using the PSLCD in computing devices and display devices.
The PSLCD having a digitizer may be fabricated by providing a first substrate having front and rear surfaces; providing a second substrate having front and rear surfaces, wherein the second substrate has a first display region in the front surface; forming a plurality of pixel electrodes in the first display region of the front surface of the second substrate; securing the front surface of the second substrate to the rear surface of the first substrate; and fabricating intersecting grids of the digitizer on at least one of the front and rear surfaces of the first and second substrates.
Before securing the front surface of the second substrate to the rear surface of the first substrate, it is preferable to surround the first display region with a sealing material to define a first surrounded region, and surround the first surrounded region with the sealing material. Therefore, when the first and second substrates are secured together, the sealing material surrounding the first surrounded region substantially prohibits the intrusion of any foreign substance.
In an alternative method, it is preferable to fabricate multiple display regions on one substrate. To accomplish this task, before securing the front surface of the second substrate to the rear surface of the first substrate, provide the second substrate to define a second display region having a second set of pixel electrodes; form pixel electrodes in the second display region of the second substrate; surround the first display region with a sealing material to define a first surrounded region; surround the second display region with the sealing material to define the first surrounded region; surround the first and second surrounded regions with the sealing material. When the first and second substrates are secured together, the sealing material surrounding the first and second surrounded regions substantially prohibits the intrusion of a foreign substance.
In the above processes, the intersecting grids of the digitizer are fabricated on at least one of the front and rear surfaces of the first and second substrates and in the first display region. Thereafter, the first and second substrates are scribed to separate the first display region from the second display region, each one of the first and second display regions having the digitizer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.